1. Field of the Invention
The present application relates to a light-emitting diode (LED), and in particular to a flip-chip type LED.
2. Description of the Related Art
A light-emitting diode (LED) is usually fabricated by forming an active layer over a substrate and depositing various conductive and semi-conductive layers over the substrate. The recombination of electron and hole can produce electromagnetic radiation (such as light) through the current at the p-n junction.
In recent years, a flip-chip type LED has gradually replaced the traditional LED. In the flip-chip packaging, electrodes and substrate of the flip-chip LED can be directly connected, thus preventing the illumination of the LED from being affected by the electrodes, and reducing the thermal resistance therebetween. Accordingly, the illumination efficiency thereof can be improved.
FIG. 1 is a sectional view of a conventional flip-chip type LED. As shown in FIG. 1, the conventional flip-chip type LED 10 comprises a substrate 10a, a first semiconductor layer 10b, an active layer 10c, a second semiconductor layer 10d, a reflecting ohmic contact layer 10e, a buffer layer 10f, a passivation layer 10g, a first electrode 10h, and a second electrode 10i. It should be understood that the reflecting ohmic contact layer 10e, such as a Ni/Ag/Pt alloy or Ni/Al/Ti alloy layer capable of conduction and light reflection, is very difficult to fabricate. Therefore, an LED which can be easily and effectively fabricated and has high illumination efficiency is needed.